1. Technical Field:
The present application relates to an electrolytic solution for electrochemical devices, such as rechargeable batteries, and an electrochemical device.
2. Description of the Related Art:
Development of portable devices such as smartphones and electric vehicles has demanded the batteries of these devices and vehicles to have a larger capacity. For example, large-capacity batteries which are already in practical use, such as lithium ion batteries, have been demanded to have a still larger capacity.
An electrochemical device which allows anions to be inserted and deinserted is expected to have a large capacity. Particularly, a fluoride ion has the characteristics of low atomic mass and high electron affinity and electrochemically stable over a large voltage range near the standard hydrogen electrode potential. Thus, it is expected that using a fluoride ion as a negative charge carrier can realize a large-capacity electrochemical device.
Japanese Laid-Open Patent Publication No. 2013-145758 discloses an electrochemical cell in which the positive electrode and the negative electrode reversibly exchange negative charge carriers. Specifically, this publication discloses an electrolytic solution in which fluorides of alkali metals, exclusive of lithium, and alkali earth metals are dissolved, and an electrochemical cell in which an electrode containing a partially-fluorinated carbonaceous material is used.
Japanese PCT National Phase Laid-Open Publication. No. 2008-543002 discloses a non-aqueous electrolytic solution which contains lithium fluoride and an anion receptor, and a lithium ion rechargeable battery which has a positive electrode and an negative electrode of graphite.
Journal of The Electrochemical Society, 154 10 A929-A936 2007 reports about production of an electrochemical cell, which uses a positive electrode containing a graphite and an electrolytic solution in which a complex of a fluoride ion and an anion receptor is dissolved, and about the results of research on the charge/discharge characteristics achieved by insertion/deinsertion of anions in/from the positive electrode.